As for sentinel or guardian i don't know wich one easier, personaly i had some difficulties along the road.
as far as i can tell is that sentinel is getting real strong when your at lv43 in my personal experience. i could have made some bad choices which would explain why i had some troubles with sentinel but i realy like being a sentinel.
so i would say pick sentinel and for the talent build i would reccomend http://www.noxxic.com. which would help you gaining a real good talent build for PvE and PVP.